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Mucin Concentration Used As Bronchitis Biomarker

Chronic bronchitis is characterized by recurring bouts of airway inflammation accompanied by a persistent cough and phlegm production. It is different from acute bronchitis, which typically develops after a cold or influenza and only lasts a few weeks.

Chronic obstructive pulmonary disease (COPD) is typified by chronic bronchitic and emphysematous components. The concentration of mucins, the proteins that make mucus thick, is abnormally high in chronic bronchitis and that high mucin concentrations are associated with disease severity in people with chronic bronchitis.

A large team of scientists working with those at University of North Carolina (Chapel Hill, NC, USA) characterized the COPD status of 917 participants from the Subpopulations and Intermediate Outcome Measures in COPD Study (SPIROMICS) using questionnaires administered to participants, chest tomography, spirometry, and examination of induced sputum. Total mucin concentrations in sputum were measured with the use of size-exclusion chromatography and refractometry. In 148 of these participants, the respiratory secreted mucins MUC5AC and MUC5B were quantitated by means of mass spectrometry. Data from chronic-bronchitis questionnaires and data on total mucin concentrations in sputum were also analyzed in an independent 94-participant cohort.

The scientists found that the mean (± SE) total mucin concentrations were higher in current or former smokers with severe COPD than in controls who had never smoked (3,166 ± 402 versus 1,515 ± 152 μg/mL) and were higher in participants with two or more respiratory exacerbations per year than in those with zero exacerbations (4,194 ± 878 versus 2,458 ±113 μg/mL). The absolute concentrations of MUC5B and MUC5AC in current or former smokers with severe COPD were approximately three times as high and 10 times as high, respectively, as in controls who had never smoked. The study is significant not only because it suggests mucins can be used as a biomarker for diagnosing and predicting the risk for chronic bronchitis, but also because it offers new scientific tools to measure mucin concentrations.

Mehmet Kesimer, PhD, an associate professor of pathology and laboratory medicine and the lead author of the study, said, “We really wanted to see if we could use this measure to predict risk, in the same way that we use cholesterol measurements to predict cardiovascular disease. We plan to look for ways to translate our findings into a practical test that could find its way into your doctor's office, not just for chronic bronchitis but also for other muco-obstructive diseases of the lung, such as bronchiectasis and asthma.” The study was published on September 7, 2017, in The New England Journal of Medicine.